The present invention relates to apparatus for grinding materials such as livestock feed. More particularly, the present invention relates to improved livestock feed tub grinders which employ rotary hammermills to effect grinding of feed materials introduced to the hammermill section or chamber via gravity feeding through an aperture in the tub floor. The present invention is especially useful as a feed grinder for chopping and loosening compacted feed materials so as to enhance the handling, mixing and consumption characteristics of livestock ration.
Crops intended for livestock feed such as hay and the like are generally harvested into compact bales for ease of handling and storage. The compactness of such bales not only makes it difficult to mix the materials with grains, silage or other types of feed as needed for accurately balanced rations but is also more difficult for the livestock to consume. Further, the compactness of such bales causes greater wastage of the feed from trampling and scattering by the livestock. Accordingly, various devices have been developed for grinding the bales of livestock feed so as to loosen it and break up clumps thereof into sizes more easily handled by the livestock. Such prior art devices frequently employ a rotating hammermill located below a tub-like container so as to be fed through an aperture in the bottom floor of the container. The sidewalls of the tub grinder container are rotated so as to urge the feed materials over the aperture for gravity introduction to the hammermill chamber. The hammermill itself generally is composed of a plurality of discs which are arrayed along a drive shaft and coupled to a prime mover apparatus for rotary motion. The discs are interconnected by a plurality of spaced bars on which are mounted a series of blade-like hammers for relatively free pivotal movement. Thus, the discs are intended to be rotated at a relatively constant angular velocity, while the freely pivoting hammers impact the feed to be ground and impart a grinding and cutting operation thereon.
Although rotary hammermill tub grinders for livestock feed have been in use for some time, various problems associated with urging the materials in a rotary direction within the tub have been encountered. One arrangement for reducing the so-called bridging effect of such feed materials over the aperture of the hammermill chamber is shown in the cross-referenced copending application Ser. No. 539,821 by Barcell. Despite improvements to the rotary feeding within the tub as provided by the cross-referenced Barcell invention, problems have still remained resulting from heavy and tightly compacted unground material jamming against the hammermill thereby slowing or stopping it and effectively preventing grinding of the feed. This is sometimes referred to as a slugging problem which has two essential aspects.
First, the rotary hammermill is generally positioned within a basket-like screen container which is attached below the tub floor aperture. Thus heavy and compact clumps of unground material can fall into the chamber defined by this screen thereby wedging between the discs and the container. The result is a braking effect to the hammermill so as to substantially reduce or stop its rotation. Another aspect of the slugging problem is the downward pressure by the compacted bales against the tops of the discs of the hammermill which likewise can act as a brake to the hammermill rotation. The slugging of the hammermill need not completely stop rotation of the disc but, if sufficient to prevent pivoting of the hammer elements, is still effective for stopping or significantly reducing any grinding of the feed materials. One arrangement for attempting to overcome this slugging problem is shown in U.S. Pat. No. 3,743,191 by Anderson wherein a series of fixed fingers extend downwardly into the aperture chamber. This apparatus is partially effective for preventing the wedging of materials between the chamber screen and the hammermill discs. However, apparatus such as the Anderson device do not prevent compacted bales from resting upon the upper portion of the hammermill disc thereby reducing hammer rotation and grinding effectiveness. Still further, the downwardly projecting fixed fingers of Anderson-type devices require acceptance of a reduced number of pivoted hammer elements in order to retain sufficient spacing so as to prevent interference between the hammers and the fixed fingers.